• 대한치과기공학회지
• /
• 제42권2호
• /
• pp.99-105
• /
• 2020

Purpose: A study analysed the stress distribution of abutment screw and supporting bone of fixture by the tightening torque force of the abutment screw within clinical treatment situation for the stability of the dental implant prosthesis. Methods: The finite element analysis was targeted to the mandibular molar crown model, and the implant was internal type 4.0 mm diameter, 10.0 mm length fixture and abutment screw and supporting bone. The occlusal surface was modeled in 4 cusps and loaded 100 N to the buccal cusps. The connection between the abutment and the fixture was achieved by combining three abutment tightening torque forces of 20, 25, and 30 Ncm. Results: The results showed that the maximum stress value of the supporting bone was found in the buccal cortical bone region of the fixture in all models. The von Mises stress value of each model showed 184.5 MPa at the 20 Ncm model, 195.3 MPa in the 25 Ncm model, and 216.5 MPa in the 30 Ncm model. The contact stress between the abutment and the abutment screw showed the stress value in the 20 Ncm model was 201.2 MPa, and the 245.5 MPa in the 25 Ncm model and 314.0 MPa in the 30 Ncm model. Conclusion: The increase of tightening force within the clinical range of the abutment screw of the implant dental prosthesis was found to have no problem with the stability of the supporting bone and the abutment screw.

• 콘크리트학회지
• /
• 제6권4호
• /
• pp.102-112
• /
• 1994

콘크리트의 건조수축은 수분확산과 밀접한 관계가 있으며, 수분확산과정은 온도와 습도에 의해 많은 영향을 받는다. 또한 물-시멘트비나 골재의 품질등에 의해서도 영향을 받기 때문에 고차의 비선형성을 보인다. 이 연구에서는 먼저 시간에 따른 콘크리트내의 수분분포를 해석하는 프로그램을 개발하고, 그리고 크리이프 및 온도와 숙성도에 따른 탄성계수의 변화를 고려하여 부등건조수축 및 부등응력을 계산하는 프로그램을 개발하였다. 이 프로그램에 의한 해석값들을 BP-KX 모델에 의해 계산된 건조수축값 및 실험값과 비교하여 좋은 결과를 보여 주었으며, 콘크리트내의 응력은 시간과 위치에 따라 정량적으로 계산되었다.

• Steel and Composite Structures
• /
• 제47권2호
• /
• pp.289-296
• /
• 2023

The failure of a thin-walled tube was studied in this paper based on three failure models. Both proportional and non-proportional loading paths were applied. Proportional loading consisted of combined tension-torsion. Cyclic non-proportional loading was also applied. It was a circular out-of-phase axial-shear stress loading path. The third loading path was a combination of a constant internal pressure and a bending moment. The failure models under study were equivalent plastic strain, modified Mohr-Coulomb (Bai-Wierzbicki) and Tearing parameter models. The elasto-plastic analysis was conducted using J2 criterion and nonlinear kinematic hardening. The return mapping algorithm was employed to numerically solve the plastic flow relations. The effects of the hydrostatic stress on the plastic flow and the stress triaxiality parameter on the failure were discussed. Each failure model under study was utilized to predict failure. The failure loads obtained from each model were compared with each other. The equivalent plastic strain model was independent from the stress triaxiality parameter, and it predicted the highest failure load in the bending problem. The modified Mohr-Coulomb failure model predicted the lowest failure load for the range of the stress triaxiality parameter and Lode's angle.

• Smart Structures and Systems
• /
• 제22권6호
• /
• pp.675-687
• /
• 2018

In the previous studies on the porous rock strength the effect of pore number and its diameter is not explicitly defined. In this paper crack initiation, propagation and coalescence in Brazilian model disc containing a single cylindrical hole and or multiple holes have been studied numerically using PFC3D. In model with internal hole, the ratio of hole diameter to model diameter was varied between 0.03, 0.17, 0.25, 0.33, and 0.42. In model with multiple hole number of holes was different in various model, i.e., one hole, two holes, three holes, four holes, five holes, six holes, seven holes, eight holes and nine holes. Diameter of these holes was 5 mm, 10 mm and 12 mm. The pre-holed Brazilian discs are numerically tested under Brazilian test. The breakage load in the ring type disc specimens containing an internal hole with varying diameters is measured. The mechanism of cracks propagation in the wall of the ring type specimens is also studied. In the case of multi-hole Brazilian disc, the cracks propagation and b cracks coalescence are also investigated. The results shows that breaking of the pre-holed disc specimens is due to the propagation of radially induced tensile cracks initiated from the surface of the central hole and propagating toward the direction of diametrical loading. In the case of disc specimens with multiple holes, the cracks propagation and cracks coalescence may occur simultaneously in the breaking process of model under diametrical compressive loading. Finally the results shows that the failure stress and crack initiation stress decreases by increasing the hole diameter. Also, the failure stress decreases by increasing the number of hole which mobilized in failure. The results of these simulations were comprised with other experimental and numerical test results. It has been shown that the numerical and experimental results are in good agreement with each other.

• 디지털융복합연구
• /
• 제17권12호
• /
• pp.329-336
• /
• 2019

본 연구의 목적은 요양병원 간호사의 내·외적 통제신념과 임종간호 스트레스 및 피로관계에서 임종간호 수행수준을 알아보고 임종간호에 미치는 영향을 규명하는 서술적 조사연구이다. 요양병원 간호사 422명을 대상으로 구조화 된 설문지를 사용였다. 자료분석은 기술통계는 SPSS Win 22.0와 가설적 모형의 적합도와 연구가설 경로분석은 Amos 5.0 통계 프로그램을 이용하였다. 연구결과 요양병원 간호사의 임종간호 수행에는 임종간호 스트레스, 피로, 내적통제신념이 유의한 상관관계가 나타났으며, 내적통제신념이 높을수록 임종간호 스트레스를 덜 받고 또한 임종간호 수행이 높은 것으로 나타났다. 본 연구를 통해 요양병원 간호사의 임종간호 수행을 향상하기 위한 기초자료를 제공하고자 하였으며, 요양병원간호사의 임종간호 스트레스와 피로를 감소시킬수 있는 전략적 프로그램 개발과 임종간호를 수행하는 요양병원 간호사에게 질적인 간호수행을 할 수 있는 교육이나 업무환경 개선의 노력이 필요할 것으로 생각된다.

• 대한한방내과학회지
• /
• 제32권4호
• /
• pp.550-564
• /
• 2011

Objectives : Oxidative stress seems to play a major role in mechanisms by which ethanol causes liver injury. Previous studies have shown that treatment with Yinjinchunggan-tang (Yinchenqinggan-tang, YJCGT) has protective effects on alcoholic liver disease. The aim of this study was to investigate the protective effects of YJCGT on alcohol-induced oxidative stress. Materials and Methods : In vitro, we evaluated the inhibitory activities of YJCHT on DPPH(1,1-diphenyl-2-picryl-hydrazyl), xanthine oxidase, trypsin, and hyaluronidase. In a cell culture model, we measured cell viability and proliferation, and the activities of superoxide dismutase (SOD), and catalase (CAT) after YJCGT treatment in C34 and E47 cell lines, and HepG2 cells transfected with/ without cytochrome P450IIE1 (CYP2E1) gene. In vivo, we estimated serum level of hepatic biochemical markers, and alcohol concentration in the blood. Results : YJCGT showed significant free radical scavenging activity against DPPH and xanthine oxidase and decreased hyaluronidase activity effectively in vitro. YJCGT also increased cell viability, and proliferation in C34 and in E47 cell lines, and increased activities of superoxide dismutase, and catalase in C34 and in E47 cell lines. YJCGT reduced serum AST, LDH, and total cholesterol level in some of the results, and reduced blood alcohol concentration in vivo, as well. Conclusions : This study suggests that YJCGT has protective effects on oxidative stress by inhibiting alcohol-induced suppression of antioxidant enzyme activities.

• 대한한방내과학회지
• /
• 제32권2호
• /
• pp.243-258
• /
• 2011

Objectives : This study investigated the hypolipidemic and antioxidant effects of Curcuma radix using a rat model induced by poloxamer 407 injection. Methods : Serum lipid parameters and oxidative stress-associated biomarkers were determined. Additionally, hepatic cholesterol and triglyceride as well as lipid metabolism-associated gene expressions were observed in hepatic tissue. Results : 1. Curcuma radix ameliorated elevation of serum cholesterol, triglyceride, LDL-cholesterol, MDA, hepatic cholesterol level, and reduction of serum TAC, SOD, GSH, GSH-reductase level. 2. Curcuma radix augmented up-regulated ACAT gene expression. 3. Curcuma radix almost completely ameliorated down-regulated CYP-7A1 but up-regulated HMG-CoA gene expression. Conclusions : The hypolipidemic and antioxidant properties of Curcuma radix were evidenced. This study provides a scientific basis for the clinical application of Curcuma radix and development of hypolipidemics using this herb in the future.

• 한국심리학회지 : 문화 및 사회문제
• /
• 제21권3호
• /
• pp.299-315
• /
• 2015

본 연구는 군 적응에 영향을 미치는 것으로 연구된 자기존중감, 통제소재, 사회적 지지, 스트레스 대처 방식의 요인들의 관련성을 살펴보고 구조 모형을 검증함으로써 군 적응에 대한 이해를 증진하고자 하였다. 본 연구의 대상은 강원도 소재 육군 소속 이병에서 병장까지의 현역 병사 447명이었다. 본 연구에서 사용된 측정도구는 다음과 같다. 자기 보고식 질문지를 통해서 자기존중감, 통제소재, 사회적 지지, 스트레스 대처 방식, 군 적응이 측정되었다. 신뢰도 검사를 통해 각 척도의 신뢰도를 측정하였고, 변인 간의 상관관계분석을 시행하였으며 연구모형 검증을 위해 구조방정식 모형 검증을 사용하였다. 본 연구의 결과를 다음 두 가지로 요약할 수 있다. 첫째, 자기존중감, 내적 통제와 같은 내적 특성이 각각 사회적 지지와 적극적 대처에 정적 영향을 미치며, 적극적 대처, 사회적 지지가 군 적응에 정적인 영향을 미치는 것으로 나타났다. 둘째, 내적 통제, 자기존중감이 사회적 지지와 적극적 대처를 통해 군 적응에 영향을 미친다. 이는 사회적 지지와 적극적 대처 방식이 내적 특성과 군 적응 사이의 매개 변인의 역할을 함을 밝힌 것이다. 본 연구는 개인의 내적 특성과 적응 간의 연구들에 제한점을 주는 것으로 사회적 지지 체계의 확립이나 대처 행동 훈련과 같은 개입의 중요성을 강조한다.

• Structural Engineering and Mechanics
• /
• 제2권3호
• /
• pp.245-256
• /
• 1994

A new axisymmetric crack model is proposed on the basis of p-version of the finite element method limited to theory of small scale yielding. To this end, axisymmetric stress element is formulated by integrals of Legendre polynomial which has hierarchical nature and orthogonality relationship. The virtual crack extension method has been adopted to calculate the stress intensity factors for 3-D axisymmetric cracked bodies where the potential energy change as a function of position along the crack front is calculated. The sensitivity with respect to the aspect ratio and Poisson locking has been tested to ascertain the robustness of p-version axisymmetric element. Also, the limit value that is an exact solution obtained by FEM when degree of freedom is infinite can be estimated using the extrapolation equation based on error prediction in energy norm. Numerical examples of thick-walled cylinder, axisymmetric crack in a round bar and internal part-thorough cracked pipes are tested with high precision.

• 한국압력기기공학회 논문집
• /
• 제11권1호
• /
• pp.79-86
• /
• 2015

The purpose of this study is to evaluate structural integrity of a weldment which is partially screwed and then welded. Two finite element models are constructed and solved: operating temperature and internal pressure are considered in the first simple model, and welding process and normal operating condition including heat-up process are simulated in the second model. Structural integrity assessment criteria are satisfied with both finite element models, therefore the repair weldment finely sustains structural integrity of this assembly and prevents leakage. Stresses are dramatically increased when weld residual stress is considered, but it should be considered as a secondary stress.